The present invention refers to a laundering process to be carried out in a domestic laundering machine, as well as to a domestic laundering machine of the type having a perforated basket mounted inside a tank.
In some of the known constructions of laundering machines, the washing operation occurs by agitating the washing liquid (water and detergent) contained inside a perforated basket of said machine, in which is immersed a load of clothes.
The machine starts the laundering process by feeding the washing liquid to the inside of the tank wherein is mounted the perforated basket, until a determined liquid level is reached, corresponding to a certain liquid volume, which is previously defined for washing the load of clothes placed therein. The amount of washing liquid varies with the load of clothes to be washed and, in some appliances, it may be selected according to said load of clothes.
After being filled, the laundering machine starts its washing operation, with a static soaking step, in which the clothes remain, for a determined time interval, in an inert condition and immersed in the washing liquid, before the washing operation is started, with the agitation of the load of clothes and washing liquid (washing load).
In one of the known laundering machine constructions which comprises the tank and the perforated basket with a vertical shaft, the washing is carried out, after the soaking step, by agitating the washing load inside the perforated basket, said agitation being provided by a central agitator, which is for example provided with radial vanes and which reciprocates during the washing process. The agitator acts simultaneously over the washing liquid and mechanically and directly over the clothes immersed in said liquid. The alternate angular movement is transmitted to the agitator from an electric motor, which is operatively coupled to said agitator through a driving shaft.
In this type of washing operation, each reversal of the rotation direction of the agitator occurs after the latter is caused to make an angular displacement which is smaller than a full turn around its rotation shaft.
The movement of the agitator in each rotation direction during the washing operation is determined so as to guarantee a relative movement between the washing liquid and the clothes immersed therein inside the perforated basket. This relative movement is what allows the clothes to be cleaned, since it forces the washing liquid to pass through said clothes.
The washing efficiency is directly related to the agitation pattern, to its agitation rate (number of back and forth movements by time unit), to the rotation angle of the agitator and to the agitator speed (which is determined by the type of motor and reducing rates). The agitation pattern should be set in order to reach a balance regarding the motor effort, dirt removal and wear of the clothes being washed.
After the washing step, the clothes are subjected to a centrifugal step, in order to extract the excess of water and obtain a pre-drying condition.
During the period in which the load of clothes remains in the soaking step, the detergent contained in the water-detergent mixture precipitates onto said load, where it remains until the agitation of the washing step is started. During this period, the detergent which precipitates on the clothes starts reacting therewith, initiating the cleaning process. However, due to the stationary condition in which are found the clothes immersed in the washing liquid during the soaking step, only a certain amount of the detergent will react with the dirt to be removed from the clothes, said reacted detergent and the dirt remaining trapped in the clothes, preventing the non-reacted detergent, which is present in the washing liquid, from reacting with the clothes and improving the cleaning effect.
Besides impairing the cleaning efficiency, the known laundering processes further have the disadvantage of permitting, during the soaking step, the occurrence of stains in the soaked clothes to be cleaned. Since the load of clothes may not be fully immersed in the washing liquid, part of said non-immersed clothes which is in contact with the environmental air inside the laundering machine cabinet will not be subjected, during the soaking step, to the reactions with the detergent of the washing liquid. The difference between the washing liquid and the environmental air mediums may cause stains in the pieces of the soaked clothes which are only partially submerged.
Thus, it is an object of the present invention to provide a laundering process for a laundering machine having a perforated basket for containing clothes, which optimizes the cleaning of the pieces of a washing load during the soaking step of the laundering process, which allows for a better use of the reactant of the washing liquid and which minimizes the occurrence of stains in said washing load caused by the difference of exposure of said load to the washing liquid medium and to the environmental air medium inside the cabinet of the laundering machine. Another object of the present invention is to provide a laundering machine, which operates according to the above laundering process and which affords obtaining an optimized cleaning of the load of clothes placed in said machine.
These and other objectives are attained through a laundering process for a laundering machine, which comprises a tank for containing a washing liquid and a perforated basket for containing the clothes and which is internal to said tank, said laundering process comprising a washing step, in which the washing liquid has at least one predetermined washing level and, in general, one centrifugal step, said laundering process including a soaking step, which precedes the washing step and which comprises the following phases: a)xe2x80x94automatically feeding the tank with the washing liquid, until reaching a determined soaking level, which is lower than a respective washing level; and b)xe2x80x94submitting the load of clothes immersed in the washing liquid, alternately, to a resting condition, during a resting period, and to an agitation condition, during at least one agitation period, which is shorter than the resting period, the washing step comprising an initial phase of feeding the tank with washing liquid, until the washing level has been completed.